A wide variety of configurations of intervertebral implants have been utilized for stabilizing adjacent vertebral elements and facilitating the development of bone union between the vertebral elements. In some configurations, the intervertebral implants are not adjustable by the surgeon during the surgical procedure. Therefore, the surgeon must choose the size that most closely matches the desired dimensions. Because these implants are of a pre-determined size and shape, the implant site must correspond to the implant configuration. This can require extensive site preparation to complete implantation. Extensive site preparation can compromise the success of the implantation procedure by causing excessive damage to the receiving vertebral elements. In addition, procedures requiring extensive site preparation can result in relatively long surgeries that may increase patient risk.
To address this problem, more recent intervertebral implants have been designed to expand from a first height to a second height. One such intervertebral implant is described in U.S. Pat. No. 6,174,334. This implant includes a pair of shells that when assembled form an implant assembly. Teeth are formed on each shell so that the shells can be uni-directionally spaced apart.
In general, improvement has been sought with respect to implantation procedures and devices, generally to provide an expandable implant assembly that reduces the invasiveness of the procedure and to provide an expandable implant that is easily adjusted during an implantation procedure.